package com.simple.behavior.classandclass.observer;

/**
 * @author simple
 * @version 1.0
 * @date 2019-01-04 17:06
 * @since 1.0
 * @see java.util.Observable
 */
public interface Subject {
    void add(Observer observer);

    void del(Observer observer);

    void notifyObservers();

    void operation();
}
